Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>

using namespace std;

int h, w, d;
char field[51][51];
int dist[51][51];

int main() {
	const int INF = 1 << 29;
	cin >> h >> w;
	int white_count = 0;
	for (int i = 0;i < h;i++) {
		for (int j = 0; j < w;j++) {
			cin >> field[i][j];
			dist[i][j] = INF;
			if (field[i][j] == '.')
				white_count++;
		}
	}

	dist[0][0] = 0;
	queue<pair<int,int>> q;
	q.push({ 0,0 });
	while (q.size()) {
		int y = q.front().first;
		int x = q.front().second;
		q.pop();
		const int dy[] = { 0,1,0,-1 };
		const int dx[] = { 1,0,-1,0 };
		for (int i = 0;i < 4;i++) {
			int ny = y + dy[i];
			int nx = x + dx[i];
			if (ny >= 0 && nx >= 0 && ny < h&&nx < w&&dist[ny][nx] == INF && field[ny][nx] == '.') {
				dist[ny][nx] = dist[y][x] + 1;
				q.push({ ny,nx });
			}
		}
	}
	if (dist[h - 1][w - 1] == INF) {
		cout << -1 << endl;
	}
	else {
		cout << white_count - (dist[h - 1][w - 1]+1) << endl;
	}

	return 0;
}